E32 Heater Problem

[Larry F.]

Our '88 Hartge 735i (with a stick) is having a heater problem. In short, puny heat. Engine is at normal temp (sez my laser-guided pyrometer) and temp guage is at a comfortable 11 o'clock when warmed up. And, the engine warms up reasonably quickly. If you don't run the heat for a while and "surprise" the heater by turning on the fan, the air is hot for a bit, then chills out. Sustained air flow cools off consistantly.

From all this I presume greatly reduced water flow. My question is, how to troubleshoot whether it is the dual heater control valve assy - $$$ - or the whole electronic climate control assy -$$$$$$- (count more dollar signs)?

Any thoughts?

[DAGERM50]

change the heater core

[Larry F.]

In the meantime (since I had posted my query) I have discovered the problem. It turns out that my very early E32 has the heater valves that can be rebuilt, like the ones in E28's. It has two valve assy's for the driver and passenger sides. I discovered this when I was trying to find a part number on the valve assy - I was about to buy a new one, and my car being a Euro, there were lots of variables to consider.

In any event, when I pulled the covers to look for the part number (which I never did find!) I recognized the rebuildable valves from my E28 experience! Joy! I pulled them out (you don't even have to drain the coolant - just crack the reserviour cap to release any pressure) and they had the classic failure mode I had seen before: rotted rubber diaphram on just one side, which means the valve will not open. So I cleaned all the parts (gummy) put the best combo of parts on the driver's side of the valve, and viola! Heat again! The driver's side is almost normal, a good thing, since the temp here has been in the teens for the last week. I ordered the rebuild parts (they are about $20 a set from Pelican - many thanks to Bobby) and I should get the new ones in tomorrow or so.

So no core, no way, no thanks!